bfd_cleanup for object_p

The object_p (and archive_p, core_file_p) functions are not supposed
to have any target specific malloc'd memory attached to the bfd on
their return.  This should be obvious on a failure return, but it's
also true for a successful return.  The reason is that even though the
object_p recognises the file, that particular target may not be used
and thus the bfd won't be closed calling close_and_cleanup for the
target that allocated the memory.

It turns out that the object_p bfd_target* return value isn't needed.
In all cases except ld/plugin.c the target is abfd->xvec and with
ld/plugin.c the target isn't used.  So this patch returns a cleanup
function from object_p instead, called in bfd_check_format_matches to
tidy the bfd before trying a different target match.  The only cleanup
that does anything at this stage is the alpha-vms one.

bfd/
	* targets.c (bfd_cleanup): New typedef.
	(struct bfd <_bfd_check_format>): Return a bfd_cleanup.
	* libbfd-in.h (_bfd_no_cleanup): Define.
	* format.c (bfd_reinit): Add cleanup parameter, call it.
	(bfd_check_format_matches): Set cleanup from _bfd_check_format
	call and pass to bfd_reinit.  Delete temp, use abfd->xvec instead.
	* aout-target.h (callback, object_p): Return bfd_cleanup.
	* aout-tic30.c (tic30_aout_callback, tic30_aout_object_p): Likewise.
	* archive.c (bfd_generic_archive_p): Likewise.
	* binary.c (binary_object_p): Likewise.
	* coff-alpha.c (alpha_ecoff_object_p): Likewise.
	* coff-ia64.c (ia64coff_object_p): Likewise.
	* coff-rs6000.c (_bfd_xcoff_archive_p, rs6000coff_core_p): Likewise.
	* coff-sh.c (coff_small_object_p): Likewise.
	* coff-stgo32.c (go32_check_format): Likewise.
	* coff64-rs6000.c (xcoff64_archive_p, rs6000coff_core_p),
	(xcoff64_core_p): Likewise.
	* coffgen.c (coff_real_object_p, coff_object_p): Likewise.
	* elf-bfd.h (bfd_elf32_object_p, bfd_elf32_core_file_p),
	(bfd_elf64_object_p, bfd_elf64_core_file_p): Likewise.
	* elfcode.h (elf_object_p): Likewise.
	* elfcore.h (elf_core_file_p): Likewise.
	* i386msdos.c (msdos_object_p): Likewise.
	* ihex.c (ihex_object_p): Likewise.
	* libaout.h (some_aout_object_p): Likewise.
	* libbfd-in.h (bfd_generic_archive_p, _bfd_dummy_target),
	(_bfd_vms_lib_alpha_archive_p, _bfd_vms_lib_ia64_archive_p): Likewise.
	* libbfd.c (_bfd_dummy_target): Likewise.
	* libcoff-in.h (coff_object_p): Likewise.
	* mach-o-aarch64.c (bfd_mach_o_arm64_object_p),
	(bfd_mach_o_arm64_core_p): Likewise.
	* mach-o-arm.c (bfd_mach_o_arm_object_p),
	(bfd_mach_o_arm_core_p): Likewise.
	* mach-o-i386.c (bfd_mach_o_i386_object_p),
	(bfd_mach_o_i386_core_p): Likewise.
	* mach-o-x86-64.c (bfd_mach_o_x86_64_object_p),
	(bfd_mach_o_x86_64_core_p): Likewise.
	* mach-o.c (bfd_mach_o_header_p, bfd_mach_o_gen_object_p),
	(bfd_mach_o_gen_core_p, bfd_mach_o_fat_archive_p): Likewise.
	* mach-o.h (bfd_mach_o_object_p, bfd_mach_o_core_p),
	(bfd_mach_o_fat_archive_p, bfd_mach_o_header_p): Likewise.
	* mmo.c (mmo_object_p): Likewise.
	* pef.c (bfd_pef_object_p, bfd_pef_xlib_object_p): Likewise.
	* peicode.h (coff_real_object_p, pe_ILF_object_p),
	(pe_bfd_object_p): Likewise.
	* plugin.c (ld_plugin_object_p, bfd_plugin_object_p): Likewise.
	* ppcboot.c (ppcboot_object_p): Likewise.
	* rs6000-core.c (rs6000coff_core_p): Likewise.
	* som.c (som_object_setup, som_object_p): Likewise.
	* srec.c (srec_object_p, symbolsrec_object_p): Likewise.
	* tekhex.c (tekhex_object_p): Likewise.
	* vms-alpha.c (alpha_vms_object_p): Likewise.
	* vms-lib.c (_bfd_vms_lib_archive_p, _bfd_vms_lib_alpha_archive_p),
	(_bfd_vms_lib_ia64_archive_p, _bfd_vms_lib_txt_archive_p): Likewise.
	* wasm-module.c (wasm_object_p): Likewise.
	* xsym.c (bfd_sym_object_p): Likewise.
	* xsym.h (bfd_sym_object_p): Likewise.
	* aoutx.h (some_aout_object_p): Likewise, and callback parameter
	return type.
	* pdp11.c (some_aout_object_p): Likewise.
	* plugin.c (register_ld_plugin_object_p): Update object_p
	parameter type.
	* plugin.h (register_ld_plugin_object_p): Likewise.
	* bfd-in2.h: Regenerate.
	* libbfd.h: Regenerate.
	* libcoff.h: Regenerate.
ld/
	* plugin.c (plugin_object_p): Return a bfd_cleanup.
	(plugin_cleanup): New function.

bfd/peicode.h

@@ -122,7 +122,7 @@ typedef struct
 pe_ILF_vars;
 #endif /* COFF_IMAGE_WITH_PE */
 
-const bfd_target *coff_real_object_p
+bfd_cleanup coff_real_object_p
   (bfd *, unsigned, struct internal_filehdr *, struct internal_aouthdr *);
 
 #ifndef NO_COFF_RELOCS
@@ -1142,7 +1142,7 @@ pe_ILF_build_a_bfd (bfd *	    abfd,
 /* We have detected a Image Library Format archive element.
    Decode the element and return the appropriate target.  */
 
-static const bfd_target *
+static bfd_cleanup
 pe_ILF_object_p (bfd * abfd)
 {
   bfd_byte	  buffer[14];
@@ -1300,7 +1300,7 @@ pe_ILF_object_p (bfd * abfd)
       return NULL;
     }
 
-  return abfd->xvec;
+  return _bfd_no_cleanup;
 }
 
 static void
@@ -1394,7 +1394,7 @@ pe_bfd_read_buildid (bfd *abfd)
   free (data);
 }
 
-static const bfd_target *
+static bfd_cleanup
 pe_bfd_object_p (bfd * abfd)
 {
   bfd_byte buffer[6];
@@ -1404,7 +1404,7 @@ pe_bfd_object_p (bfd * abfd)
   struct internal_aouthdr internal_a;
   bfd_size_type opt_hdr_size;
   file_ptr offset;
-  const bfd_target *result;
+  bfd_cleanup result;
 
   /* Detect if this a Microsoft Import Library Format element.  */
   /* First read the beginning of the header.  */